Experts from Harvard T.H. Chan School of Public Health have found that girls who eat more high-fibre foods during adolescence - especially lots of fruits and vegetables - may have significantly lower breast cancer risk than those who eat less dietary fibre when young, According to their research, for each additional 10 grams of fibre intake daily - for example, about one apple and two slices of whole wheat bread, or about half a cup each of cooked kidney beans and cooked cauliflower or squash - during early adulthood, breast cancer risk drops by 13 percent.
"From many other studies we know that breast tissue is particularly influenced by carcinogens and anti-carcinogens during childhood and adolescence," said senior author of the study Walter Willett, professor at Harvard T.H. Chan School of Public Health.
"We now have evidence that what we feed our children during this period of life is also an important factor in future cancer risk," Willett noted.
The researchers believe that eating more fibre-rich foods may lessen breast cancer risk partly by helping to reduce high estrogen levels in the blood, which are strongly linked with breast cancer development. The study was be published online in the journal Pediatrics.
"This work on the role of nutrition in early life and breast cancer incidence suggests one of the very few potentially modifiable risk factors for pre-menopausal breast cancer," lead author of the study Maryam Farvid noted.
The researchers looked at a group of 90,534 women who participated in the Nurses' Health Study II, a large long-running investigation of factors that influence women's health. Breast cancer risk was 12-19 percent lower among women who ate more dietary fibre in early adulthood, depending on how much more they ate, the study said. The greatest apparent benefit came from fruit and vegetable fibre.
In particular, greater consumption of apple, banana and grapes during adolescence, as well as oranges and kale during early adulthood was significantly associated with a reduced breast cancer risk, said the researchers. But there was no link between the intake of fruit juice in either adolescence or early adulthood and risk, they said.
In the second study, a team of Danish researchers wanted to test the effect of a change in alcohol intake on the risk of breast cancer and heart disease. They followed the health of nearly 22,000 post-menopausal women in Denmark and found that those who increased their alcohol intake by two drinks per day over five years had around a 30 per cent increased risk of breast cancer but around a 20 per cent decreased risk of coronary heart disease, compared with women with a stable alcohol intake.
However, results for women who decreased their alcohol intake over the five year period were not significantly associated with risk of breast cancer or coronary heart disease.
"There may be some benefit with low to moderate intakes of alcohol, but this could be outweighed by an increased risk of breast cancer and other morbidities," said researchers.